Cockpit (https://cockpit-project.org) and its builtin set of UIs for system services has become an integral part of Fedora Server, RHEL, and is included in all major distributions.
It has always been very simple to create your own interfaces using Cockpit's API. But it is a big step from some quick HMTL+JS proof of concept towards maintaining a production-grade project with proper integration testing/gating and fully automatic delivery. This talk introduces the tools and services that the Cockpit team offers for developing your Cockpit extensions, which gets you there right from scratch.